An optical device comprising an anode, a cathode comprising barium, strontium or calcium, and a layer of organic semiconducting material between the anode and the cathode wherein a layer of hole transporting and electron blocking material is located between the anode and the layer of organic semiconducting...http://www.google.de/patents/US7531831?utm_source=gb-gplus-sharePatent US7531831 - Electroluminescent device comprising a cross-linked hole transporting and electron blocking material
